Spark plug cooling means



July 27, 1943. P. 5. ANDRES SPARK PLUG COOLING MEANS Filed April 24,1941 iwm O P EN 0 fi w m. 4 am, m i Y E Patented July 27, 1943 SPARKPLUG COOLING MEANS Paul G. Andres, Oak Park, Ill., assignor to BowcsSeal Fast Corporation, Indianapolis, Ind., a corporation of IndianaApplication April 24, 1941, Serial No. 390,061

Claims.

This invention relates to spark plugs of the type employed in automotivepractice for engine ignition. With the advent of the high compression,high speed engines and particularly under the heavy duty imposed onaviation engines, small details in construction of spark plugs have cometo involve major problems and have been found to vitally affect thedurability and life of the plugs. Furthermore, due to several factors,one of which is reduction in weight per horsepower output of theengines, spark plugs have been reduced in dimensions in order to fitwithin the limited spaces permitted, and yet are required to give ahigher degree of reliable performance than heretofore.

It has been found that a major problem involved in the design of areliable spark plug is that of dissipation or rather distribution ofheat. It is possible for the nose of the porcelain insulator of thecommonly provided central electrode to run too hot and it is alsoequally possible for that nose to run too cold. Again it has been foundthat in the spark plug commonly employed heretofore, the gap between theshell electrode and the central insulated electrode will varyconsiderably due to temperature changes. In these prior constructions ofspark plugs, it has been the usual practice to employ a round shellelectrode welded or otherwise secured by one end to the lowermost end ofthe shell and then bend that electrode around and under the centralelectrode. This meant that the shell electrode at all times had a bendin it which would cause the gap between it and the central electrode tovary on account of subsequent relieving of stresses under expansion andcontraction. Furthermore, there was no possibility of making a fixed gapdimension in manufacture of the plug since the exposed shell electrodewas subject to being shifted under storage and transportation conditionsdue to impact.

A further difficulty found to exist in these prior types of spark plugsis that in order to place the shell electrode at the proper position inrelation to the wall of the combustion chamber, it was necessary toprovide a supporting shell normally less than the length of the threadedhole into which the shell was threaded. This reduced length of shell inrelation to the length of the threaded hole, of course, reduced the areaof contact between the shell and the water surrounded part of the enginethrough which the threaded hole was provided, meaning that the rate ofheat dissipation was reduced.

Also what may now see to be a simple solution of heat transfer has beendiscovered to be of utmost importance, and a solution also offering anadditional advantage over and above the accelerated heat dissipation.This solution relates to the seating of a highly heat conductive gasketaround the shell of the plug to be compressed between it and the enginewall not only to seal against escape of gases but also to form a quickheat dissipating zone. This gasket becomes in effect an integral part ofthe shell so that when the spark plug is removed from the engine, thegasket is not left down in a well as is the usual case but is withdrawnwith the spark plug so that upon replacing the plug, there is nopossibility remaining of a new gasket being placed over an old gasketdown in that well, a situation which would affect the positioning of theelectrodes of the plug.

It is the primary purpose of my invention to overcome the difficultiesabove enumerated in a very simple and readily constructed mechanism aswill hereinafter be set forth. Other important objects and advantages ofthe invention will become apparent to those versed in the art in thedescription which is made in reference to the accompanying drawing, inwhich Fig. 1 is a view in side elevation of a spark plug embodying theinvention and shown in a mounted position;

Fig. 2, a view in end elevation of the nose of the plug, on a greatlyenlarged scale; and

Fig. 3, a central diametrical section on the line 3-3 in Fig. 2 throughthe threaded end of the plug.

Like characters of reference indicate like parts in the several views inthe drawing.

The spark plug, generally designated by the numeral ID, has the usualporcelain insulator Ii sealably mounted in the metallic shell I2 fromwhich extends a threaded end portion l3 to be screw-threadedly enteredinto a hole provided in an engine head or wall 14, The invention hereinset forth involves primarily the lower part of the plug Ill.

The threaded end I3 is given a length in every instance which will carryit entirely through the bore in the wall l4 so that this end I3 willalways have the greatest possible area of contact through its threadedsurface with the surface of the bore within which it is carried.

The lower end of this portion i3 carries a short straight electrode barl5, herein shown as I rectangular in cross sect on. The lower end of toreceive therein the nose of the insulator II) so as to receive the outerend of the bar I5 therein preferably by a forced fit, following whichthe bar I5 is electrically welded to the portion I3. The bar I5 extendshorizontally, in reference to the drawing herein, across under the lowerend of the central electrode I6 that projects beyond the lower end ofthe insulator I I, Fig. 3. Thus it is to be seen that there is no bendwhatsoever in the bar I5, and furthermore, the under side of this bar I5is flush with the terminating end of the shell portion I3. To allintents and purposes, the electrode bar I5 becomes an integral part ofthe shell end I3. The spacing between the lower end of the centralelectrode I6 and the bar I5 may be predetermined and fixed inmanufacturing. Since the bar I5 extends within the bore within the endportion I3, there is very little likelihood of its spacing from theelectrode I5 being changed accidentally.

At the upper end of the threaded portion I3, the shell is given anoutwardly extending tapered shoulder I! from which extends upwardly ashort cylindrical surface I8. The diameter of this surface I8 is made tobe slightly greater than the normal internal diameter of the sealinggasket I9. This gasket I9, while it may take any desired form, is hereinshown as of the usual type which consists of a sheet of copper foldedover on itself and finished in the form of a ring.

The threaded end plug portion I3 is entered through the gasket I9 andscrew-threadedly engaged in the bore through the wall I4. By drawing theplug I down snugly, the inclined or beveled surface II will be carriedthrough the gasket I9 tending first to center it around the plug andthen tending to expand the gasket so that continued downward travel ofthe plug will eventually force the gasket I9 up and around thecylindrical surface I8 to have the gasket I9 eventually come against theflat seat 20 provided around the plug.

The gasket I9, of course, resists expansion under this action and isforcibly carried onto the surface I9 with the result that the gasket issnugly fitted against the fiat face 20 in intimate contact therewith andis given an even greater intimate contact with the surface l8. In fact,

practice shows that it is quite difficult to remove the gasket I9 fromthis seated position since the gasket becomes in effect a fixed part ofthe plug.

Now in service, a plug constructed as above described will have the gapbetween the end of the electrode I6 and the top side of the shellelectrode I positioned substantially in the plane of the inner side ofthe wall I4 and at the same time the threaded portion I3 will be carrieddown to that inside face of the wall I4. This means that heat arisingfrom combustion of gases causing the spark plug to be heated thereby isprevented from unduly heating the lower end of the plug by reason of thefact that heat received by the electrode I5 is rapidly conducted intothe threaded portion I3 without having to travel through or around bendstherein and begins to be dissipated at, the very lowest part of thethreaded end of the plug which, as above indicated, is at the inner faceof the wall I4. The wall I4 is, of course, as indicated in Fig. 1,covered over by water and this water space extends up and around thepart through which the threaded portion I3 extends. Further, as the heatis transmitted along the threaded portion I3, it is further and morequickly dissipated through the gasket I9 at t e top of thewater-jacketed part so as to aid in preventing travel of the heatupwardly into the larger mass of metal of the shell I2. In other wordsthere is a cool ring interposed between the lower threaded portion I3and the upper mass of the shell. This ring, as above indicated, isautomatically placed in position and into effect simply by screwing theplug into operating position on the engine.

This heat control and travel is obtained without, in the presentinstance, affecting the heat control of the nose of the porcelaininsulator II. In other words the electrode I5 and its supporting shellportion I3 may have the temperatures thereof effectively controlledindependently of the temperature of the electrode I6 and its supportinginsulator I I.

While I have herein shown and described my invention in the one preciseform, it is obvious that structural changes may be employed withoutdeparting from the spirit of the invention and I therefore do not desireto be limited to that precise form beyond the limitations as may beimposed by the following claims.

I claim:

1. For an engine having a water jacketed wall through which extends aspark plug receiving bore, a spark plug having a metallic shell; acentral insulator carried thereby; a central electrode carried by theinsulator; a lower shell end portion threaded exteriorly and having. aninternal bore receiving said central electrode therein, said end portionextending below the lower end of said electrode; a straight shellelectrode bar having one end inserted within a slot in and integrallyunited with said portion to extend in a straight transverse directioninto the bore of said portion to leave a spark gap between it and saidcentral electrode; and means forming a rapid heat dissipation zonearound the upper end of said lower shell portion; whereby heat may bedissipated with minimum travel through said shell electrode to said walland limited in upward travel in said shell by said zone.

2. For an engine having a water jacketed wall through which extends aspark plug receiving bore, a spark plug having a metallic shell; acentral insulator carried thereby; a central electrode carried by theinsulator; a lower shell end portion threaded exteriorly and having aninternal bore receiving said central electrode therein, said end portionextending below th lower end of said electrode; a straight shellelectrode bar having one end inserted within a slot in and integrallyunited with said portion to extend in a straight transverse directioninto the bore of said portion to leave a spark gap between it and saidcentral electrode; and means forming a rapid heat dissipation zonearound the upper end of said lower shell portion; whereby heat may bedissipated with minimum travel through said shell electrode to said walland limited in upward travel in said shell by said zone; said heatdissipating zone means comprising a high heat conducting collarintimately attached to said shell to be compressively held against saidwall by said plug.

3. For an engine having a water jacketed wall through which extends aspark plug receiving bore, a spark plug having a metallic shell; acentral insulator carried thereby; a central electrode carried by theinsulator; a lower shell end portion threaded exteriorly and having aninternal bore receiving said central electrode therein, said end portionextending below the lower end of said electrode; a straight shellelectrode bar having one end inserted within a slot in and integrallyunited with said portion to extend in a straight transverse directioninto the bore of said portion to leave a spark gap between it and saidcentral electrode; and means forming a rapid heat dissipation zonearound the upper end of said lower shell portion; whereby heat may bedissipated with minimum travel through said shell electrode to said walland limited in upward travel in said shell by said zone, said insulatorbeing spaced within and from the wall of said threaded portionthroughout its length.

4. For an engine having a water jacketed wall through which extends aspark plug receiving bore, a spark plug having a metallic shell; acentral insulator carried thereby; a central electrode carried by theinsulator; a lower shell end portion threaded exteriorly and having aninternal bore receiving said central electrode therein, said end portionextending below the lower end of said electrode; a straight shellelectrode bar having one end inserted within a slot in and integrallyunited with said portion to extend in a, straight transverse directioninto the bore of said portion to leave a spark gap between it and saidcentral electrode; and means forming a rapid heat dissipation zonearound the upper end of said lower shell portion; whereby heat may bedissipated with minimum travel through said shell electrode to said walland limited in upward travel in said shell by said zone; said shellelectrode being rigid and of sufficient cross-sectional area to resistbending under temperature changes.

5. For an engine having a water jacketed wall through which extends aspark plug receiving bore, a spark plug having a metallic shell; acentral insulator carried thereby; a central electrode carried by theinsulator; a lower shell end portion threaded exteriorly and having aninternal bore receiving said central electrode therein, said end portionextending below the lower end of said electrode; a straight shellelectrode bar having one end inserted within a slot in and integrallyunited with said portion to extend in a straight transverse directioninto the bore of said portion to leave a spark gap between it and saidcentral electrode; and means forming a rapid heat dissipation zonearound the upper end of said lower shell portion; whereby heat may bedissipated with minimum travel through said shell electrode to said walland limited in upward travel in said shell by said zone; said shellelectrode being confined within said lower shell por- :7

tion.

6. For an engine having a water jacketed wall through which extends aspark plug receiving bore, a spark plug having a metallic shell; acentral insulator carried thereby; a central electrode carried by theinsulator; a lower shell end portion threaded exteriorly and having aninternal bore receiving said central electrode therein, said end portionextending below the lower end of said electrode; a straight shellelectrode bar having one end inserted within a slot in and integrallyunited with said portion to extend in a straight transverse directioninto the bore of said portion to leave a spark gap between it and saidcentral electrode; and means forming a rapid heat dissipation zonearound the upper end of said lower shell portion; whereby heat may bedissipated with minimum travel through said shell electrode to said walland limited in upward travel in said shell by said zone; said shellelectrode being confined within said lower shell portion, the under sideof the shell electrode being in a plane of the lower end of that shellportion.

'7. For an engine having a water jacketed wall through which extends aspark plug receiving bore, a spark plug having a metallic shell; acentral insulator carried thereby; a central electrode carried by theinsulator; a lower shell end portion threaded exteriorly and having aninternal bore receiving said central electrode therein, said end portionextending below the lower end of said electrode; a straight shellelectrode bar having one end integrally united with said portion toextend in a straight transverse direction into the bore of said portionto leave a spark gap between it and said central electrode; and meansforming a rapid heat dissipation zone around the upper end of said lowershell portion; whereby heat may be dissipated with minimum travelthrough said shell electrode to said wall and limited in upward travelin said shell by said zone; said electrode shell consisting of a flatbar welded by its said end within a rectangular slot in the shellportion.

8. For an engine having a water jacketed wall through which extends aspark plug receiving bore, a spark plug having a metallic shell; acentral insulator carried thereby; a central electrode carried by theinsulator; a hollow, threaded, lower shell end portion extending belowthe lower end of said electrode; a straight shell electrode bar havingone end inserted within a slot in and integrally united with saidportion to extend in a straight transverse direction into said portionto leave a spark gap between it and said central electrode; and meansforming a rapid heat dissipation zone around the upper end of said lowershell portion; whereby heat may be dissipated with minimum travelthrough said shell electrode to said wall and limited in upward travelin said shell by said zone; said shell electrode being confined withinsaid lower shell portion, the under side of the shell electrode being ina plane of the lower end of that shell portion; said central electrodeterminating by its lower end above said shell electrode.

9. In a spark plug having a metallic shell, a central insulator carriedthereby, an electrode extending axially through the insulator, thecombination of a lower threaded end shell portion; an electrodeextending from the shell portion to form a spark gap between it and saidcentral electrode; an upwardly and outwardly flaring shoulder at theupper end of said threaded portion terminating by a maximum diametersubstantially equal to at least the external diameter of said threadedend portion; a cylindrical area extending upwardly from said shoulderand having a diameter at least equal to that of said maximum shoulderdiameter; a gasket compressing seat carried by said shell portion at theupper end of said cylindrical area, said seat extending outwardly fromsaid cylindrical area in a plane substantially normal to the plug axis;a ring-like metallic gasket initially having a minimum internal diameterless than that of said cylindrical area; said gasket being elasticallystretched around said cylindrical area and frictionally engagedtherewith below said seat.

10. In a spark plug having a metallic shell, a central insulator carriedthereby, an electrode extending axially through the insulator, thecombination of a lower threaded end shell portion; an electrodeextending from the shell portion to form a spark gap between it and saidcentral electrode; an upwardly and outwardly flaring shoulder at theupper end of said threaded portion terminating by a maximum diametersubstantially equal to at least the external diameter of said threadedend portion; a cylindrical area ex-- tending upwardly from said shoulderand having a diameter at least equal to that of said maximum shoulderdiameter; a gasket compressing seat carried by said shell portion at theupper end of said cylindrical area, said seat extending outwardly fromsaid cylindrical area in a plane substantially normal to the plug axis;a ring-like metallic gasket initially having a minimum internal diameterless than that of said cylindrical area: said gasket being elasticallystretched around said cylindrical area and frictionally engagedtherewith below said seat; said gasket being formed of a high heatconducting material and its external diameter being limitedsubstantially to that of said seat, the upper face of said gasket beinglimited in elevation to that of said 10 seat.

PAUL G. ANDRES.

